Evaporator

ABSTRACT

An evaporator includes a pair of header tanks spaced from each other in a vertical direction; a plurality of flat heat exchange tubes  45  which are disposed between the two header tanks such that their width direction coincides with a front-rear direction and they are spaced from one another in a left-right direction, opposite ends portions of the flat heat exchange tubes being connected to the corresponding header tanks; and corrugated fins  5  each disposed between adjacent heat exchange tubes  45 . Each of left and right portions of front and rear end walls  45   a  of each heat exchange tube  45  has a straight slope portion  55  which inclines outward in the front-rear direction, toward a center portion of the heat exchange tube  45  with respect to the left-right direction. The angle formed between the slope portion  55  and the left edge or right edge of the corresponding corrugated fin  5  is set to 25 to 40 degrees.

TECHNICAL FIELD

The present invention relates to an evaporator suitable for use in a carair conditioner, which is a refrigeration cycle to be mounted on anautomobile, for example.

In this specification and the appended claims, the downstream side (adirection represented by arrow X in FIGS. 1, 2, 8, and 10) of an airflow through air-passing clearances between adjacent heat exchange tubeswill be referred to as the “front,” and the opposite side as the “rear.”Further, the upper, lower, left-hand, and right-hand sides of FIG. 1will be referred to as “upper,” “lower,” “left,” and “right,”respectively.

BACKGROUND ART

The present applicant has proposed an evaporator for a car airconditioner which satisfies the requirements for reduction in size andweight and higher performance (refer to Patent Document 1). Theevaporator includes a pair of header tanks spaced from each other in thevertical direction; a plurality of flat heat exchange tubes which areformed of aluminum extrudate and which are disposed between the twoheader tanks such that their width direction coincides with thefront-rear direction and they are spaced from one another in thelongitudinal direction of the header tanks, opposite ends portions ofthe flat heat exchange tubes being connected to the corresponding headertanks; and corrugated fins each disposed between adjacent heat exchangetubes and having louvers. The upper header tank includes a refrigerantinlet header section and a refrigerant outlet header section, which arejuxtaposed in the front-rear direction and are united together. Thelower header tank includes a first intermediate header section disposedto face the refrigerant inlet header section, and a second intermediateheader section disposed rearward of the first intermediate headersection to face the refrigerant outlet header section and united withthe first intermediate header section. The upper and lower end portionsof the front heat exchange tubes are connected to the refrigerant inletheader section and the first intermediate header section, respectively,and the upper and lower end portions of the rear heat exchange tubes areconnected to the refrigerant outlet header section and the secondintermediate header section. Each of the front and rear end walls ofeach heat exchange tube has an arcuate transverse cross sectionprojecting outward with respect to the front-rear direction.

Since the evaporator described in Patent Document 1 is designed tosatisfy the requirements for reduction in size and weight and higherperformance, a large amount of condensed water is produced on thesurface of each corrugated fin, whereby the amount of condensed waterper unit volume of the evaporator increases. Incidentally, an ordinaryevaporator is designed such that water condensed on the fin surfaceflows downward through clearances between adjacent louvers. Therefore,in order to enhance water draining performance, increasing the length ofthe louvers is desirable. However, in order to reduce size and weight asin the case of the evaporator described in Patent Document 1, theclearance between heat exchange tubes located adjacent to each other inthe longitudinal direction of the header tanks must be reduced.Therefore, there is a limit on increasing the length of the louvers, andwater draining performance may become insufficient when the amount ofcondensed water is large.

PRIOR ART DOCUMENT Patent Document

-   Patent Document 1: Japanese Patent Application Laid-Open (kokai) No.    2008-20098

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

An object of the invention is to solve the above-described problem, andprovide an evaporator which has an excellent performance of drainingwater condensed on the surfaces of fins.

Means for Solving the Problems

To achieve the above object, the present invention comprises thefollowing modes.

1) An evaporator comprising a pair of header tanks spaced from eachother in a vertical direction; a plurality of flat heat exchange tubeswhich are disposed between the two header tanks such that their widthdirection coincides with a front-rear direction and they are spaced fromone another in a left-right direction, opposite ends portions of theflat heat exchange tubes being connected to the corresponding headertanks; and corrugated fins each disposed between adjacent heat exchangetubes, wherein

each of left and right portions of front and rear end walls of each heatexchange tube has a straight slope portion which inclines outward in thefront-rear direction, toward a center portion of the heat exchange tubewith respect to the left-right direction, and an angle formed betweenthe slope portion and a left edge or right edge of the correspondingcorrugated fin is 25 to 40 degrees.

2) An evaporator according to par. 1), wherein left and right sidesurfaces of each heat exchange tube are in contact with thecorresponding corrugated fins; and a ratio of a length W2 (mm), asmeasured in the front-rear direction, of areas of contact between theleft and right side surfaces of the heat exchange tube and thecorresponding corrugated fins to a width W1 (mm) of each heat exchangetube as measured in the front-rear direction is 80 to 95%.

3) An evaporator according to par. 1), wherein each heat exchange tubehas a width of 10 to 20 mm as measured in the front-rear direction.

4) An evaporator according to par. 1), wherein each heat exchange tubehas a thickness of 1 to 1.8 mm as measured in the left-right direction.

5) An evaporator according to par. 1), wherein a plurality of tube setseach composed of a plurality of flat heat exchange tubes spaced from oneanother in the front-rear direction are disposed between the upper andlower header tanks at predetermined intervals in the left-rightdirection; each of the fins is disposed between tube sets locatedadjacent to each other in the left-right direction; and, in each tubeset composed of a plurality of the flat heat exchange tubes, a clearanceis formed between the heat exchange tubes located adjacent to each otherin the front-rear direction, the clearance having a width of 1.5 to 3.5mm as measured in the front-rear direction.

6) An evaporator according to par. 1), wherein each heat exchange tubeis provided in a flat hollow body composed of two pressed rectangularmetal plates laminated and joined together; the two metal plates whichconstitute the flat hollow body are bulged outward so as to form theheat exchange tube such that the heat exchange tube is open at upper andlower ends thereof; each of front and rear walls of an outward bulgedportion of each metal plate which forms the heat exchange tube isstraight and inclines outward in the front-rear direction, toward athicknesswise center portion of the flat hollow body.

7) An evaporator according to par. 6), wherein, at a front edge of eachflat hollow body, one of the two metal plates has a protrusion formedover the entire length thereof such that a distal end portion of theprotrusion projects beyond the other metal plate and toward thecorrugated fin with which the other metal plate is in contact.

Effects of the Invention

According to the evaporators of par. 1) to 7), each of left and rightportions of the front and rear end walls of each heat exchange tube hasa straight slope portion which inclines outward in the front-reardirection, toward a center portion of the heat exchange tube withrespect to the left-right direction, and the angle formed between theslope portion and the left edge or right edge of the correspondingcorrugated fin is 25 to 40 degrees. Therefore, recesses are formedbetween the slope portions of the front and rear end walls of each heatexchange tube and the left and right edges of the correspondingcorrugated fins such that a corner portion of each recess located on theinner side with respect to the width direction of the heat exchange tubehas an acute angle. Thus, due to surface tension, condensed waterproduced on the surfaces of the corrugated fins flows into the recessesas if it were drawn into the recesses, and flows downward through therecesses. Accordingly, the evaporator has an improved performance ofdraining the condensed water produced on the surfaces of the corrugatedfins, whereby scattering of condensed water and a drop in heat exchangeperformance caused by freezing of condensed water are prevented.

According to the evaporator of par. 2), it is possible to restrain adrop in heat conduction performance caused by a decrease in the areas ofcontact between the heat exchange tubes and the corrugated fins, withoutpreventing the flow of the condensed water into the recesses formedbetween the slope portions of the front and rear end walls of each heatexchange tube and the left and right edges of the correspondingcorrugated fins.

According to the evaporator of par. 5), in each tube set composed of aplurality of flat heat exchange tubes disposed between the two headertanks, a clearance is formed between the heat exchange tubes locatedadjacent to each other in the front-rear direction, and the clearancehas a width of 1.5 to 3.5 mm as measured in the front-rear direction.Thus, due to surface tension, condensed water produced on the surfacesof the corrugated fins flows into the clearances between the heatexchange tubes of each tube set located adjacent to each other in thefront-rear direction, as if it were drawn into the clearances, and flowsdownward through the clearances. Accordingly, the evaporator has animproved performance of draining the condensed water produced on thesurfaces of the corrugated fins, whereby scattering of condensed waterand a drop in heat exchange performance caused by freezing of condensedwater are prevented.

According to the evaporator according to par. 6), the straight slopeportions—which incline outward in the front-rear direction, toward acenter portion of the heat exchange tube with respect to the left-rightdirection—can be relatively easily formed at the left and right portionsof the front and rear end walls of each heat exchange tube. Also, theangle formed between each slope portion and the left edge or right edgeof the corresponding corrugated fin can be relatively easily set to 25to 40 degrees.

According to the evaporator according to par. 7), scattering ofcondensed water from the front edge of each flat hollow body can beprevented.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially cut-away perspective view showing the overallstructure of an evaporator according to a first embodiment of thepresent invention.

FIG. 2 is a partially omitted enlarged sectional view taken along lineA-A of FIG. 1.

FIG. 3 is an enlarged sectional view taken along line B-B of FIG. 2.

FIG. 4 is a graph showing the results of Experimental Examples 1 to 2and Comparative Experimental Examples 1 to 2.

FIG. 5 is a graph relating to Experimental Examples 1 to 2 andComparative Experimental Example 1 and showing the relation among theamount of retained water, contact ratio, and angle between slopeportions of each heat exchange tube and left and right edges ofcorresponding corrugated fins.

FIG. 6 is a graph relating to Experimental Examples 1 to 2 andComparative Experimental Example 1 and showing the relation between theratio of the amount of retained water to the contact ratio obtained fromthe graph of FIG. 5, and the angle between slope portions of each heatexchange tube and left and right edges of corresponding corrugated fins.

FIG. 7 is a graph showing the results of Experimental Examples 3 to 4and Comparative Experimental Examples 3 to 4.

FIG. 8 is a view corresponding to FIG. 2 and showing an evaporatoraccording to a second embodiment of the present invention.

FIG. 9 is a partially omitted enlarged sectional view taken along lineC-C of FIG. 8.

FIG. 10 is a view corresponding to FIG. 2 and showing an evaporatoraccording to a third embodiment of the present invention.

FIG. 11 is a partially omitted enlarged sectional view taken along lineD-D of FIG. 10.

DESCRIPTION OF REFERENCE NUMERALS

-   (1), (60), (90): evaporator-   (2), (3), (61), (62): header tank-   (4), (63): flat hollow body-   (5): corrugated fin-   (41), (75): metal plate-   (43), (95): clearance-   (44), (92): set of heat exchange tubes juxtaposed in the front-rear    direction-   (48), (78): outward bulged portion-   (48 a), (78 a): front and rear walls-   (45), (76), (91): heat exchange tube-   (45 a), (76 a), (91 a): front and rear end walls-   (55), (83), (93): slope portion-   (57), (85): protrusion

MODES FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will next be described withreference to the drawings. Like portions and members are denoted by likereference numerals throughout the drawings, and repeated description isnot provided.

In the following description, the term “aluminum” encompasses aluminumalloys in addition to pure aluminum.

First Embodiment

This embodiment is shown in FIGS. 1 to 3. FIG. 1 shows the overallstructure of an evaporator, and FIGS. 2 and 3 show the structure of amain portion of the evaporator.

As shown in FIGS. 1 and 2, an evaporator (1) includes a first headertank (2) and a second header tank (3) formed of aluminum and disposedapart from each other in the vertical direction such that they extend inthe left-right direction; a plurality of flat hollow bodies (4) formedof aluminum and disposed between the two header tanks (2) and (3) atpredetermined intervals in the left-right direction (the longitudinaldirection of the header tanks (2) and (3)) such that their widthdirection coincides with the front-rear direction and their longitudinaldirection coincides with the vertical direction; louvered, corrugatedfins (5) made of aluminum, disposed in air-passing clearances betweenthe adjacent flat hollow bodies (4) and externally of the left- andright-end flat hollow bodies (4), and brazed to the flat hollow bodies(4); and side plates (6) made of aluminum, disposed externally of theleft- and right-end corrugated fins (5) and brazed to the corrugatedfins (5).

The first header tank (2) includes a refrigerant inlet header section(7) located on the front side (downstream side with respect to the airflow direction) and extending in the left-right direction; a refrigerantoutlet header section (8) located on the rear side (upstream side withrespect to the air flow direction) and extending in the left-rightdirection; and a connection section (9) which integrally connects theheader sections (7) and (8) together. A refrigerant inlet pipe (11) madeof aluminum is connected to the refrigerant inlet header section (7) ofthe first header tank (2). Similarly, a refrigerant outlet pipe (12)made of aluminum is connected to the refrigerant outlet header section(8). The second header tank (3) includes a first intermediate headersection (13) located on the front side and extending in the left-rightdirection; a second intermediate header section (14) located on the rearside and extending in the left-right direction; and a connection section(15) which integrally connects the header sections (13) and (14)together.

The first header tank (2) is composed of a plate-like first member (16)which is formed, through press work, from an aluminum brazing sheethaving a brazing material layer on each of opposite sides thereof and towhich all the flat hollow bodies (4) are connected; a second member (17)which is formed, through press work, from an aluminum brazing sheethaving a brazing material layer on each of opposite sides thereof andwhich covers the upper side of the first member (16); a flat partitionportion forming plate (18) which is formed, through press work, from analuminum brazing sheet having a brazing material layer on each ofopposite sides thereof or an aluminum bear material and which isinterposed between the first member (16) and the second member (17) andis brazed to the two members (16) and (17); left and right end members(19) which are formed, through press work, from an aluminum brazingsheet having a brazing material layer on each of opposite sides thereofand which are brazed to the left ends and right ends, respectively, ofthe first member (16), the second member (17), and the partition portionforming plate (18); and a joint plate (21) which is formed of aluminum,extends in the front-rear direction, and is brazed to the outer surfaceof the right end member (19) such that the joint plate (21) extendsacross the refrigerant inlet header section (7) and the refrigerantoutlet header section (8). The refrigerant inlet pipe (11) and therefrigerant outlet pipe (12) are connected to the joint plate (21).Notably, the joint plate (21) is formed from an aluminum bear materialthrough press work.

The first member (16) has front and rear downward-bulged header formingportions (22) and (23) which form lower portions of the refrigerantinlet header section (7) and the refrigerant outlet header section (8);and a connection wall (24) which connects the front and rear headerforming portions (22) and (23) together and forms a lower portion of theconnection section (9). A plurality of tube insertion holes (25)elongated in the front-rear direction are formed in the two headerforming portions (22) and (23) of the first member (21) at predeterminedintervals in the left-right direction such that the positions (withrespect to the left-right direction) of the tube insertion holes (25)formed in the front header forming portion (22) coincide with those ofthe corresponding tube insertion holes (25) formed in the rear headerforming portion (23).

The second member (17) has front and rear upward-bulged header formingportions (26) and (27) which form upper portions of the refrigerantinlet header section (7) and the refrigerant outlet header section (8);and a connection wall (28) which connects the front and rear headerforming portions (26) and (27) together and forms an upper portion ofthe connection section (9).

The partition portion forming plate (18) has a front partition portion(29) which divides the interior of the refrigerant inlet header section(7) into upper and lower spaces (7A) and (7B); a rear partition portion(31) which divides the interior of the refrigerant outlet header section(8) into upper and lower spaces (8A) and (8B); and a connection wall(32) which connects the two partition portions (29) and (31) together,and forms an intermediate portion (with respect to the verticaldirection) of the connection section (9). A communication hole (33) forestablishing communication between the upper and lower spaces (7A) and(7B) within the refrigerant inlet header section (7) is formed in thefront partition portion (29) of the partition portion forming plate (18)at a position located leftward of the flat hollow body (4) disposed atthe left end. A plurality of circular communication holes (34) forestablishing communication between the upper and lower spaces (7A) and(7B) of the refrigerant inlet header section (7) are formed in anintermediate portion (with respect to the front-rear direction) of thefront partition portion (29) of the partition portion forming plate (18)at predetermined intervals in the left-right direction. Further, aplurality of oblong communication holes (35) elongated in the left-rightdirection and adapted to establish communication between the upper andlower spaces (8A) and (8B) of the refrigerant outlet header section (8)are formed, at predetermined intervals in the left-right direction, in arear portion of the rear partition portion (31) of the partition portionforming plate (18), excluding left and right end portions of the rearportion. The length of the oblong communication hole (35) in the centralportion is shorter than those of the remaining oblong communication hole(35).

The left end member (19) closes the left end openings of the refrigerantinlet header section (7) and the refrigerant outlet header section (8),and the right end member (19) closes the right end openings of therefrigerant inlet header section (7) and the refrigerant outlet headersection (8). Although not illustrated in the drawings, a refrigerantinlet is formed in a portion (facing the upper space (7A)) of a portionof the right end member (19) which portion closes the right end openingof the refrigerant inlet header section (7), and a refrigerant outlet isformed in a portion (facing the upper space (8A)) of a portion of theright end member (19) which portion closes the right end opening of therefrigerant outlet header section (8). The joint plate (21) hasrefrigerant passages which communicate with the refrigerant inlet andthe refrigerant outlet of the right end member (19).

The second header tank (3) has a structure similar to that of the firstheader tank (2), and is disposed upside down with respect to the firstheader tank (2). Therefore, like portions are denoted by like referencenumerals.

Notably, the two header forming portions (22) and (23) of the firstmember (16) of the second header tank (3) form upper portions of thefirst intermediate header section (13) and the second intermediateheader section (14), and the two header forming portions (26) and (27)of the second member (17) of the second header tank (3) form lowerportions of the first intermediate header section (13) and the secondintermediate header section (14). Also, the interior of the firstintermediate header section (13) is divided into upper and lower spaces(13A) and (13B) by the front partition portion (29) of the partitionportion forming plate (18), and the interior of the second intermediateheader section (14) is divided into upper and lower spaces (14A) and(14B) by the rear partition portion (31) of the partition portionforming plate (18). Furthermore, an intermediate portion of theconnection portion (15) with respect to the vertical direction is formedby the connection wall (32) of the partition portion forming plate (18).

The second header tank (3) differs from the first header tank (2) in thefollowing points.

The first difference is that a plurality of communication portions (36)for establishing communication between the lower space (13B) of thefirst intermediate header section (13) and the lower space (14B) of thesecond intermediate header section (14) are provided at predeterminedintervals (with respect to the left-right direction) in a portion of thesecond member (17) which portion separates the lower spaces (13B) and(14B) of the two intermediate header sections (13) and (14) from eachother. The communication portions (36) are provided at a plurality oflocations such that each communication portion (36) is provided betweentwo flat hollow bodies (4) located adjacent to each other with respectto the left-right direction and such that the amount of refrigerantwithin the second intermediate header section (14) can be made uniformalong the longitudinal direction of the second header tank (3).

The second difference is that, in place of the communication hole (33)and the circular communication holes (34), a plurality of relativelylarge rectangular communication holes (37) elongated in the left-rightdirection are formed in the front partition portion (29) of thepartition portion forming plate (18) at predetermined intervals in theleft-right direction; and that, in place of the oblong communicationholes (34), a plurality of circular communication holes (through holes)(38) are formed in a rear portion of the rear partition portion (31) ofthe partition portion forming plate (18) at predetermined intervals inthe left-right direction.

The third difference is that the refrigerant inlet and the refrigerantoutput are not formed in the right end member (21), and the joint plate(21) is not brazed thereto.

As shown in FIGS. 2 and 3, each of the flat hollow bodies (4) is formedthrough a process of making two rectangular metal plates (41) from analuminum brazing sheet through press working, and brazing the tworectangular metal plates (41), over the entire length thereof, alongfront and rear edge portions thereof and along center portions thereofwith respect to the front-rear direction. Each of the flat hollow bodies(4) has two heat exchange tubes (45), the number of which is equal tothe number of the header sections (7) and (8) of the first header tank(2) and the number of the header sections (13) and (14) of the secondheader tank (3). The heat exchange tubes (45) extend in the verticaldirection, and are open at the upper and lower ends thereof. The heatexchange tubes (45) of each flat hollow body (4) are provided throughformation of outward bulged portions (48) on the two metal plates (41)over the entire length thereof in regions between brazed portions (46)of the front and rear edge portions of the two metal plates (41), andbrazed portions (47) of the center portions (with respect to thefront-rear direction) of the two metal plates (41). The heat exchangetubes (45) have a flat shape such that their width direction coincideswith the front-rear direction. Each flat hollow body (4) has a tube set(44) including a plurality of (two in the present embodiment) of flatheat exchange tubes (45) whose width direction coincides with thefront-rear direction and which are spaced from each other in thefront-rear direction. In each tube set (44), clearances (43) are formedbetween the heat exchange tubes (45) located adjacent to each other inthe front-rear direction. That is, a plurality of tube sets (44)—eachcomposed of a plurality of flat heat exchange tubes (45) disposed suchthat their width direction coincides with the front-rear direction andthey are spaced from one another in the front-rear direction—aredisposed between the first header tank (2) and the second header tank(3) at predetermined intervals in the left-right direction; and each ofthe corrugated fins (5) is disposed between the tube sets (44) (sets ofthe heat exchange tube (45)) located adjacent to each other in theleft-right direction.

Upper and lower end portions of the brazed portions (46) of the frontand rear edge portions of the two metal plates (41) of each flat hollowbody (4) are cut such that the formed cutouts extend from the outeredges with respect to the front-rear direction to the upper and lowerend surfaces, respectively. The cutouts are denoted by (51). Also, upperand lower end portions of the brazed portions (47) of the centerportions (with respect to the front-rear direction) of the two metalplates (41) of each flat hollow body (4) have a width (as measured inthe front-rear direction) greater than those of the remaining portions,and cutouts (52) are formed in wide brazed portions (47 a) such that thecutouts (52) extend from the respective outer ends with respect to thevertical direction. Notably, due to provision of the width brazedportions (47 a) on each flat hollow body (4), upper and lower endportions of each heat exchange tube (45) is narrower than the reamingportions as measured in the front-rear direction. As a result offormation of the cutouts (51) in the brazed portions (46) of the frontand rear edge portions and formation of the cutouts (52) in the widthbrazed portions (47 a) of the center portions with respect to thefront-rear direction, the upper and lower end portions of each heatexchange tube (45) project outward with respect to the verticaldirection from the remaining portions. The projecting portions serve asinsertion portions (53) inserted into the tube insertion holes (25) ofthe first header tank (2) and the second header tank (3). The flathollow bodies (4) are brazed to the first members (16) of the two headerthanks (2) and (3) as follows. The upper and lower insertion portions(53) of the front heat exchange tubes (45) are inserted into the fronttube insertion holes (25) of the first members (16) of the first headertank (2) and the second header tank (3). Similarly, the upper and lowerinsertion portions (53) of the rear heat exchange tubes (45) areinserted into the rear tube insertion holes (25) of the first members(16) of the first header tank (2) and the second header tank (3). At thetime of the insertion operation, bottom side portions of the cutouts(51) of the brazed portions (46) of the front and rear edge portions ofeach flat hollow body (4) and bottom side portions of the cutouts (52)of the width brazed portions (47 a) of the center portions of the flathollow body (4) are brought into contact with the outer surfaces of thetwo header forming portions (22) and (23) of the respective firstmembers (16) of the first header tank (2) and the second header tank(3), whereby the end portions of the flat hollow bodies (4) arepositioned. In this state, the flat, hollow bodies (4) are brazed to thefirst members (16) of the first header tank (2) and the second headertank (3). The corrugated fins (5) are shared by the front and rear heatexchange tubes (45) of the corresponding flat hollow bodies (4). Thecrest portions or trough portions of each corrugated fin (5) are brazedto the corresponding heat exchange tube (45). Also, a plurality oflouvers are formed on connection portions of each corrugated fin (5)located between the crest portions and trough portions thereof.Moreover, a corrugated inner fin (54) formed of aluminum is disposed ineach flat hollow body (4) such that the corrugated inner fin (54)extends through the interiors of the two heat exchange tubes (45), andis brazed to the two metal plates (41).

Straight slope portions (55) are provided on left and right portions offront and rear end walls (45 a) of the two heat exchange tubes (45) ofeach flat hollow body (4). The straight slope portions (55) inclineoutward with respect to the front-rear direction, toward the centerportions of the heat exchange tubes (45) (with respect to the left-rightdirection). That is, front and rear walls (48 a) of the outward bulgedportions (48) of the metal plates (41) of each flat hollow body (4),which portions form the two heat exchange tubes (45), linearly inclinein an outward direction with respect to the front-rear direction, towardthe thicknesswise center of the flat hollow body (4). Thus, recessportions (56) are formed between the outer surfaces of the slopeportions (55) of the front and rear end walls (45 a) of the heatexchange tubes (45) of each flat hollow body, and the left and rightedge portions of the corresponding corrugated fins (5). A corner portionof each recess (56) located on the inner side with respect to the widthdirection of the heat exchange tubes (45) has an acute angle. The angleθ formed between each of the slope portions (55) of the front and rearend walls (45 a) of the two heat exchange tubes (45) and the left orright edge portion of the corresponding corrugated fin (5) is set to 25to 40 degrees in consideration of drainage of water condensed on thesurfaces of the flat hollow bodies (4) and the corrugated fins (5).Also, when the width of the heat exchange tubes (45) as measured in thefront-rear direction is represented by W1 (mm) and the length (asmeasured in the front-rear direction) of contact areas where the leftand right side surfaces of the heat exchange tubes (45) are in contactwith the corresponding corrugated fins (5) is represented by W2 (mm),preferably, a contract ratio W2/W1; i.e., the ratio of W2 (the length(as measured in the front-rear direction) of the areas of contactbetween the left and right side surfaces of the heat exchange tubes (45)and the corresponding corrugated fins (5)) to W1 (the width of the heatexchange tubes (45) as measured in the front-rear direction), is 80 to95%. Furthermore, preferably, the width W1 of the heat exchange tubes(45) as measured in the front-rear direction is 10 to 20 mm, and thethickness H of the heat exchange tubes (45) as measured in theleft-right direction is 1 to 1.8 mm.

At each of the front and rear edges of each flat hollow body (4), aprotrusion (57) is formed on one of the two metal plates (41) over theentire length thereof such that a distal end portion of the protrusion(57) projects beyond the other metal plate (41) and toward thecorrugated fin (5) with which the other metal plate (41) is in contact.That is, a protrusion (57) whose distal end projects rightward beyondthe right metal plate (41) is formed at the front edge of the left metalplate (41) of the flat hollow body (4) over the entire length thereof,and another protrusion (57) whose distal end projects leftward beyondthe left metal plate (41) is formed at the rear edge of the right metalplate (41) of the flat hollow body (4) over the entire length thereof.

In each tube set (44) including the flat hollow bodies (4), preferably,the width S (as measured in the front-rear direction) of the clearances(43) formed between the heat exchange tube (45) located adjacent to eachother in the front-rear direction is 1.5 to 3.5 mm. If the width S ofthe clearances (43) as measured in the front-rear direction is smallerthan 1.5 mm, condensed water having been produced on the surfaces of thecorrugated fins (5) and flowed into (as if it had been drawn into) theclearances (43) between the front and rear heat exchange tubes (45) ofeach tube set (44) by means of surface tension stagnates at theclearances (43) due to surface tension, which hinders a downward flow ofthe condensed water. If the width S of the clearances (43) as measuredin the front-rear direction is greater than 3.5 mm, condensed waterproduced on the surfaces of the corrugated fins (5) becomes less likelyto be drawn into the clearances (43). Also, preferably, the thickness Hof the heat exchange tubes (45) as measured in the left-right directionis 1 to 1.8 mm, the width W of the heat exchange tubes (45) as measuredin the front-rear direction is 10 to 20 mm.

In manufacture of the evaporator (1), component members thereofexcluding the inlet pipe (11) and the outlet pipe (12) are assembledtogether, and brazed together.

The evaporator (1), together with a compressor and a condenser servingas a refrigerant cooler, constitutes a refrigeration cycle which uses achlorofluorocarbon-based refrigerant. This refrigeration cycle isinstalled in a vehicle, such as an automobile, as a car air conditioner.

In the evaporator (1) described above, while the compressor is ON, atwo-phase refrigerant of vapor-liquid phase having passed through thecompressor, the condenser, and an expansion valve enters the upper space(7A) of the refrigerant inlet header section (7) from the refrigerantinlet pipe (11); flows through the lower space (7B) of the same, thefront heat exchange tubes (45) of the flat hollow bodies (4), the upperspace (13A) of the first intermediate header section (13), the lowerspace (13B) of the same, the lower space (14B) of the secondintermediate header section (14), the upper space (14A) of the same, therear heat exchange tubes (45) of the flat hollow bodies (4), the lowerspace (8B) of the refrigerant outlet header section (8), and the upperspace (8A) of the same; and flows out to the refrigerant outlet pipe(12).

While flowing through the front and rear heat exchange tubes (45) of theflat hollow bodies (4), the refrigerant is subjected to heat exchangewith air flowing through the air-passing clearances between the adjacentflat hollow bodies (4). Then, the refrigerant flows out from theevaporator (1) in a vapor phase.

At that time, condensed water is produced on the surfaces of thecorrugated fins (5). Due to surface tension, the condensed water flowsinto the recesses (56) formed between the outer surfaces of the slopesportions (55) of the front and rear end walls (45 a) of the heatexchange tubes (45) of each flat hollow body (4) and the left and rightedges of the corresponding corrugated fins (5), as if the condensedwater were drawn into the recesses (56). After that, the condensed waterflows downward via the recesses (56). Accordingly, the evaporator (1)has an improved condensed water draining performance, whereby a drop inthe performance of the evaporator (1) is prevented. Furthermore,frontward scattering of condensed water is restrained by the action ofthe protrusion (57) at the front edge of each flat hollow body (4).

Next, experimental examples which were performed by use of the flathollow bodies (4) of the evaporator (1) according to the firstembodiment will be described along with comparative experimentalexamples.

Experimental Example 1

There was prepared an assembly which was equivalent to an assemblyobtained by removing the two header tanks (2) and (3), the refrigerantinlet pipe (11), and the refrigerant outlet pipe (12) from theevaporator (1) of the first embodiment, and in which only the flathollow bodies (4), the corrugated fins (5), and the side plates (6) werebrazed together. The angle θ between each of the slope portions (55) ofthe front and rear end walls (45 a) of the two heat exchange tubes (45)of each flat hollow body (4) and the left or right edge portion of thecorresponding corrugated fin (5) was 25 degrees. The assembly wasimmersed in water within a tank for removal of air remaining within theassembly. After that, the assembly was allowed to stand for 30 minutes.Subsequently, the assembly was lifted such the flat hollow bodies (4)became vertical, and was removed from the water. In this state, theweight of the assembly was measured for 30 minutes so as to investigatea change in the amount of retained water.

Experimental Example 2

An assembly identical with that used in Experimental Example 1 exceptthat the angle θ between each of the slope portions (55) of the frontand rear end walls (45 a) of the two heat exchange tubes (45) and theleft or right edge portion of the corresponding corrugated fin (5) wasset to 35 degrees was prepared, and a change in the amount of retainedwater was investigated in the same manner as in Experimental Example 1.Notably, the width W1 of the heat exchange tubes (45) as measured in thefront-rear direction and the thickness H of the heat exchange tubes (4)as measured in the left-right direction are the same as those of theheat exchange tubes used in the Experimental Example 1.

Comparative Experimental Example 1

An assembly identical with that used in Experimental Example 1 exceptthat the angle θ between each of the slope portions (55) of the frontand rear end walls (45 a) of the two heat exchange tubes (45) and theleft or right edge portion of the corresponding corrugated fin (5) wasset to 45 degrees was prepared, and a change in the amount of retainedwater was investigated in the same manner as in Experimental Example 1.Notably, the width W1 of the heat exchange tubes (45) as measured in thefront-rear direction and the thickness H of the heat exchange tubes (4)as measured in the left-right direction are the same as those of theheat exchange tubes used in the Experimental Example 1.

Comparative Experimental Example 2

Instead of the flat hollow bodies (4), tube pairs each composed of twoheat exchange tubes spaced from each other in the front-rear directionwere brazed together with the corrugated fins (5) and the side plates(6), whereby an assembly was prepared. The heat exchange tubes had thesame structure as that disclosed in Patent Document 1; i.e., the frontand rear end walls of the heat exchange tubes had an arcuate shape, asviewed on a transverse cross section, which was convex outward withrespect to the front-rear direction. Notably, the heat exchange tubesused in Comparative Experimental Example 2 have the same width (asmeasured in the front-rear direction) and thickness (as measured in theleft-right direction) as those of the heat exchange tubes used in theExperimental Example 1. A change in the amount of retained water wasinvestigated in the same manner as in Experimental Example 1.

FIG. 4 shows the results of Experimental Examples 1 to 2 and ComparativeExperimental Examples 1 to 2. As is clear from the results shown in FIG.4, in Experimental Examples 1 to 2, the amount of retained water afterelapse of 30 minutes is smaller as compared with ComparativeExperimental Example 1 to 2, and excellent draining performance isattained.

FIG. 5 shows the relation among the amount of retained water, thecontact ratio W2/W1, and the angle θ obtained from Experimental Example1 to 2 and Comparative Experimental Example 1. As described previously,the contract ratio W2/W1 is the ratio of W2 (the length (as measured inthe front-rear direction) of the areas of contact between the left andright side surfaces of the heat exchange tubes and the correspondingcorrugated fins) to W1 (the width of the heat exchange tubes as measuredin the front-rear direction). The angle θ is the angle between each ofthe slope portions of the front and rear end walls of the heat exchangetubes and the left or right edge portion of the corresponding corrugatedfin.

FIG. 6 shows the relation between the ratio of the water retrainingamount to the contact ratio W2/W1 and the angle θ between each of theslope portions of the front and rear end walls of the heat exchangetubes and the left or right edge portion of the corresponding corrugatedfin. The graph of FIG. 6 means that, when the ratio of the waterretraining amount to the contact ratio W2/W1 is small, it is possible torestrain a drop in heat conduction performance caused by a decrease inthe areas of contact between the heat exchange tubes and the corrugatedfins, while preventing a drop in draining performance. Accordingly, theresults shown in FIG. 6 demonstrate that, when the angle θ between eachof the slope portions of the front and rear end walls of the heatexchange tubes and the left or right edge portion of the correspondingcorrugated fin is 25 to 40 degrees, the condensed water drainingperformance can be enhanced, while a required thermal conductivity issecured.

Experimental Example 3

There was prepared an assembly which was equivalent to an assemblyobtained by removing the two header tanks (2) and (3), the refrigerantinlet pipe (11), and the refrigerant outlet pipe (12) from theevaporator (1) of the first embodiment, and in which only the flathollow bodies (4), the corrugated fins (5), and the side plates (7) werebrazed together. The width S (as measured in the front-rear direction)of the clearances (43) formed between the front and rear heat exchangetubes (45) of each flat hollow body (4) was 1.6 mm. The assembly wasimmersed in water within a tank for removal of air remaining within theassembly. After that, the assembly was allowed to stand for 30 minutes.Subsequently, the assembly was lifted such the flat hollow bodies (4)became vertical, and was removed from the water. The assembly was heldin this state for 30 minutes, and the amount of retained water afterelapse of 30 minutes was measured.

Experimental Example 4

An assembly identical with that used in Experimental Example 3 exceptthat the width S (as measured in the front-rear direction) of theclearances (43) formed between the front and rear heat exchange tubes(45) of each flat hollow body (4) was 2.8 mm was prepared, and theamount of retained water after elapse of 30 minutes was measured in thesame manner as in Experimental Example 3. Notably, the width W of theheat exchange tubes (45) as measured in the front-rear direction and thethickness H of the heat exchange tubes (45) as measured in theleft-right direction are the same as those of the heat exchange tubesused in the Experimental Example 1.

Comparative Experimental Example 3

An assembly identical with that used in Experimental Example 3 exceptthat the width S (as measured in the front-rear direction) of theclearances (43) formed between the front and rear heat exchange tubes(45) of each flat hollow body (4) was 1.0 mm was prepared, and theamount of retained water after elapse of 30 minutes was measured in thesame manner as in Experimental Example 3. Notably, the width W of theheat exchange tubes (45) as measured in the front-rear direction and thethickness H of the heat exchange tubes (45) as measured in theleft-right direction are the same as those of the heat exchange tubesused in the Experimental Example 1.

Comparative Experimental Example 4

Instead of the flat hollow bodies (4), tube pairs each composed of twoheat exchange tubes having the same structure as that of the heatexchange tubes used in the above-described Comparative ExperimentalExample 2 were brazed together with the corrugated fins (5) and the sideplates (6), whereby an assembly was prepared. Notably, the heat exchangetubes used in Comparative Experimental Example 4 have the same width (asmeasured in the front-rear direction) and thickness (as measured in theleft-right direction) as those of the heat exchange tubes used in theExperimental Example 3; and the width (as measured in the front-reardirection) of the clearances formed between the front and rear heatexchange tubes of each tube set was the same as that of the assemblyused in the Experimental Example 3. The amount of retained water afterelapse of 30 minutes was measured in the same manner as in ExperimentalExample 3.

FIG. 7 shows the results of Experimental Examples 3 to 4 and ComparativeExperimental Examples 3 to 4. As is clear from the results shown in FIG.7, in Experimental Examples 3 to 4, the amount of retained water afterelapse of 30 minutes is smaller as compared with ComparativeExperimental Example 3 to 4, and excellent draining performance isattained. Therefore, in order to enhance the water draining performanceof the evaporator, the width (as measured in the front-rear direction)of the clearances formed between the heat exchange tubes adjacent toeach other in the front-rear direction must be set to 1.5 to 3.5 mm.

Embodiment 2

This embodiment is shown in FIGS. 8 and 9. FIGS. 8 and 9 show thestructure of a main portion of an evaporator according to the presentembodiment.

As shown in FIGS. 8 and 9, an evaporator (60) includes a first headertank (61) and a second header tank (62) formed of aluminum and disposedapart from each other in the vertical direction such that they extend inthe left-right direction; a plurality of flat hollow bodies (63) formedof aluminum and disposed between the two header tanks (61) and (62) suchthat their width direction coincides with the front-rear direction andthey are spaced from one another in the left-right direction; corrugatedfins (5) made of aluminum, disposed in air-passing clearances betweenthe adjacent flat hollow bodies (63) and externally of the left- andright-end flat hollow bodies (63), and brazed to the flat hollow bodies(63); and side plates (not shown) made of aluminum, disposed externallyof the left- and right-end corrugated fins (5) and brazed to thecorrugated fins (5).

The entirety of the first header tank (61) serves as a refrigerant inletheader section (65), and the entirety of the second header tank (62)serves as a refrigerant outlet header section (66). A refrigerant inletpipe (not shown) is connected to the refrigerant inlet header section(65) of the first header tank (61), and a refrigerant outlet pipe (notshown) made of aluminum is connected to the refrigerant outlet headersection (66) of the second header tank (62).

The first header tank (61) is composed of a plate-like first member (67)which is formed, through press work, from an aluminum brazing sheethaving a brazing material layer on each of opposite sides thereof and towhich all the flat hollow bodies (63) are connected; a second member(68) which is formed, through press work, from an aluminum brazing sheethaving a brazing material layer on each of opposite sides thereof andwhich covers the upper side of the first member (67); a flat partitionportion forming plate (69) which is formed, through press work, from analuminum brazing sheet having a brazing material layer on each ofopposite sides thereof or an aluminum bear material and which isinterposed between the first member (67) and the second member (68) andis brazed to the two members (67) and (68); and left and right endmembers (not shown) which are formed, through press work, from analuminum brazing sheet having a brazing material layer on each ofopposite sides thereof and which are brazed to left ends and right ends,respectively, of the first member (67), the second member (68), and thepartition portion forming plate (69).

The first member (67) forms a lower portion of the refrigerant inletheader section (65), and the second member (68) forms an upper portionof the refrigerant inlet header section (65). A plurality of tubeinsertion holes (71) elongated in the front-rear direction are formed inthe first member (67) at predetermined intervals in the left-rightdirection. The partition portion forming plate (69) has a partitionportion (73) which divides the interior of the refrigerant inlet headersection (65) into upper and lower spaces (65A) and (65B). A plurality ofrelatively large rectangular communication holes (74) elongated in theleft-right direction are formed in each of front and rear portions ofthe partition portion (73) of the partition portion forming plate (69)at predetermined intervals in the left-right direction. The left andright end members close the left and right end openings of therefrigerant inlet header section (65). A refrigerant inlet is formed inthe left end member or the right end member at a position correspondingto the upper space (65A).

The second header tank (62) has a structure similar to that of the firstheader tank (61), and is disposed upside down with respect to the firstheader tank (61). Therefore, like portions are denoted by like referencenumerals.

Notably, the first member (67) of the second header tank (3) forms anupper portion of the refrigerant outlet header section (66), and thesecond member (68) thereof forms a lower portion of the refrigerantoutlet header section (66). The partition portion (73) of the partitionportion forming plate (69) divides the interior of the refrigerantoutlet header section (66) into upper and lower spaces (66A) and (66B).A refrigerant outlet is formed in the left end member or the right endmember at a position corresponding to the lower space (66B).

Each of the flat hollow bodies (63) is formed through a process ofmaking two rectangular metal plates (75) from an aluminum brazing sheetthrough press working, and brazing the two rectangular metal plates(75), over the entire length thereof, along front and rear edge portionsthereof. Each of the flat hollow bodies (63) has only one heat exchangetube (76), the number of which is equal to the number of the headersection (65) of the first header tank (61) and the number of the headersection (66) of the second header tank (62). The heat exchange tube (76)extends in the vertical direction, and is open at the upper and lowerends thereof. The heat exchange tube (76) of each flat hollow body (63)is provided through formation of outward bulged portions (78) on the twometal plates (75) over the entire length thereof in a region betweenbrazed portions (77) of the front and rear edge portions of the twometal plates (75). The heat exchange tube (76) has a flat shape suchthat its width direction coincides with the front-rear direction.

Upper and lower end portions of the brazed portions (77) of the frontand rear edge portions of the two metal plates (75) of each flat hollowbody (63) are cut such that the formed cutouts extend from the outeredges with respect to the front-rear direction to the upper and lowerend surfaces, respectively. The cutouts are denoted by (81). As a resultof formation of the cutouts (81) in the brazed portions (77) of thefront and rear edge portions, the upper and lower end portions of eachheat exchange tube (76) project outward with respect to the verticaldirection from the remaining portions. The projecting portions serve asinsertion portions (82) inserted into the tube insertion holes (71) ofthe first header tank (61) and the second header tank (63). The flathollow bodies (63) are brazed to the first members (67) of the twoheader thanks (61) and (62) as follows. The upper and lower insertionportions (82) of the heat exchange tubes (76) are inserted into the tubeinsertion holes (71) of the first members (67) of the first header tank(61) and the second header tank (62). At the time of the insertionoperation, bottom side portions of the cutouts (81) of the brazedportions (77) of the front and rear edge portions of each flat hollowbody (63) are brought into contact with the outer surfaces of therespective first members (67) of the first header tank (61) and thesecond header tank (62), whereby the end portions of the flat hollowbodies (63) are positioned. In this state, the flat hollow bodies (63)are brazed to the first members (67) of the first header tank (61) andthe second header tank (62). The crest portions or trough portions ofthe corrugated fins (5) are brazed to the corresponding heat exchangetube (76). Moreover, a corrugated inner fin (79) formed of aluminum isdisposed in the heat exchange tube (76) of each flat hollow body (63),and is brazed to the two metal plates (75).

Straight slope portions (83) are provided on left and right portions offront and rear end walls (76 a) of the heat exchange tube (76) of eachflat hollow body (63). The straight slope portions (83) incline outwardwith respect to the front-rear direction, toward the center portion(with respect to the left-right direction) of the heat exchange tube(76). That is, front and rear walls (78 a) of the outward bulgedportions (78) of the metal plates (75) of each flat hollow body (63),which portions form the heat exchange tube (76), linearly incline in anoutward direction with respect to the front-rear direction, toward thethicknesswise center of the flat hollow body (63). Thus, recess portions(84) are formed between the outer surfaces of the slope portions (83) ofthe front and rear end walls (76 a) of the heat exchange tube (76) ofeach flat hollow body (63), and the left and right edge portions of thecorresponding corrugated fins (5). A corner portion of each recess (84)located on the inner side with respect to the front-rear direction hasan acute angle. The angle θ formed between each of the slope portions(83) of the front and rear end walls (76 a) of each heat exchange tube(76) and the left or right edge portion of the corresponding corrugatedfin (5) is set to 25 to 40 degrees in consideration of drainage of watercondensed on the surfaces of the flat hollow bodies (63) and thecorrugated fins (5). Also, when the width of the heat exchange tube (76)as measured in the front-rear direction is represented by W1 (mm) andthe length (as measured in the front-rear direction) of contact areaswhere the left and right side surfaces of the heat exchange tube (76)are in contact with the corresponding corrugated fins (5) is representedby W2 (mm), preferably, a contract ratio W2/W1; i.e., the ratio of W2(the length (as measured in the front-rear direction) of the areas ofcontact between the left and right side surfaces of the heat exchangetube (76) and the corresponding corrugated fins (5)) to W1 (the width ofthe heat exchange tube (76) as measured in the front-rear direction), is80 to 95%. Furthermore, preferably, the width W1 of the heat exchangetube (76) as measured in the front-rear direction is 10 to 20 mm, andthe thickness H of the heat exchange tubes (76) as measured in theleft-right direction is 1 to 1.8 mm.

At each of the front and rear edges of each flat hollow body (63), aprotrusion (85) is formed on one of the two metal plates (75) over theentire length thereof such that a distal end portion of the protrusion(85) projects beyond the other metal plate (75) and toward thecorrugated fin (5) with which the other metal plate (75) is in contact.That is, a protrusion (85) whose distal end projects rightward beyondthe right metal plate (75) is formed at the front edge of the left metalplate (75) of the flat hollow body (63) over the entire length thereof,and another protrusion (85) whose distal end projects leftward beyondthe left metal plate (75) is formed at the rear edge of the right metalplate (75) of the flat hollow body (63) over the entire length thereof.

The evaporator (60), together with a compressor and a condenser servingas a refrigerant cooler, constitutes a refrigeration cycle which uses achlorofluorocarbon-based refrigerant. This refrigeration cycle isinstalled in a vehicle, such as an automobile, as a car air conditioner.

In the evaporator (60) described above, while the compressor is ON, atwo-phase refrigerant of vapor-liquid phase having passed through thecompressor, the condenser, and an expansion valve enters the refrigerantinlet header section (65) of the first header tank (61) from therefrigerant inlet pipe via the refrigerant inlet of the right end memberor the left end member; flows through the heat exchange tubes (76) andthe refrigerant outlet header section (66); and flows out to therefrigerant outlet pipe.

While flowing through the heat exchange tubes (76) of the flat hollowbodies (63), the refrigerant is subjected to heat exchange with airflowing through the air-passing clearances between the adjacent flathollow bodies (63). Then, the refrigerant flows out from the evaporator(60) in a vapor phase.

At that time, condensed water is produced on the surfaces of thecorrugated fins (5). Due to surface tension, the condensed water flowsinto the recesses (84) formed between the outer surfaces of the slopesportions (83) of the front and rear end walls (76 a) of the heatexchange tube (76) of each flat hollow body (63) and the left and rightedges of the corresponding corrugated fins (5), as if the condensedwater were drawn into the recesses (84). After that, the condensed waterflows downward via the recesses (84). Accordingly, the evaporator (60)has an improved condensed water draining performance, whereby a drop inthe performance of the evaporator (1) is prevented. Furthermore,frontward scattering of condensed water is restrained by the action ofthe protrusion (85) at the front edge of each flat hollow body (63).

Third Embodiment

This embodiment is shown in FIGS. 10 and 11. FIGS. 10 and 11 show thestructure of a main portion of an evaporator according to the presentembodiment.

As shown in FIGS. 10 and 11, an evaporator (90) includes a first headertank (2) and a second header tank (3), which have the same structures asthose of the first header tank (2) and the second header tank (3) of theevaporator (1) of the first embodiment and which are disposed apart fromeach other in the vertical direction. A plurality of tube sets (92) aredisposed between the two header tanks (2) and (3) at predeterminedintervals in the left-right directions. Each tube set (92) includes twoflat heat exchange tubes (91), the number of which is equal to thenumber of the header sections (7) and (8) of the first header tank (2)and the number of the header sections (13) and (14) of the second headertank (3). The flat heat exchange tubes (91) are formed of aluminumextrudate and disposed such that their width direction coincides withthe front-rear direction and they are spaced from each other in thefront-rear direction. Corrugated fins (5) made of aluminum are disposedin air-passing clearances between adjacent tube sets (92) each composedof the front and rear heat exchange tubes (91), and externally of theleft- and right-end tube sets (92), and brazed to the corresponding heatexchange tubes (91). Side plates (not shown) made of aluminum aredisposed externally of the left- and right-end corrugated fins (5) andbrazed to the corrugated fins (5). In each set (92) composed of two heatexchange tubes (91) adjacent to each other in the front-rear direction,a clearance (95) is formed between the two heat exchange tubes (91).

The front and rear heat exchange tubes (91) are brazed to the firstmembers (16) of the two header thanks (2) and (3) as follows. Upper andlower end portions of the front heat exchange tubes (91) are insertedinto the front tube insertion holes (25) of the first members (16) ofthe first header tank (2) and the second header tank (3). Similarly,upper and lower end portions of the rear heat exchange tubes (91) areinserted into the rear tube insertion holes (25) of the first members(16) of the first header tank (2) and the second header tank (3). Inthis state, the front and rear heat exchange tubes (91) are brazed tothe first members (16) of the first header tank (2) and the secondheader tank (3). The corrugated fins (5) are shared by the front andrear heat exchange tubes (91). The crest portions or trough portions ofeach corrugated fin (5) are brazed to the corresponding heat exchangetube (91).

Straight slope portions (93) are provided on left and right portions offront and rear end walls (91 a) of each heat exchange tube (91). Thestraight slope portions (93) incline outward with respect to thefront-rear direction, toward the center portion of the heat exchangetube (91) with respect to the left-right direction. Portions of thefront and rear end walls (91 a) between the two slope portions (93) areorthogonal to the left and right edges of the corrugated fins (5). Thus,recess portions (94) are formed between the outer surfaces of the slopeportions (93) of the front and rear end walls (91 a) of each heatexchange tube (91) and the left and right edge portions of thecorresponding corrugated fins (5). A corner portion of each recess (94)located on the inner side with respect to the width direction of theheat exchange tubes (91) has an acute angle. The angle θ formed betweeneach of the slope portions (93) of the front and rear end walls (91 a)of each heat exchange tubes (91) and the left or right edge portion ofthe corresponding corrugated fin (5) is set to 25 to 40 degrees inconsideration of drainage of water condensed on the surfaces of the heatexchange tubes (91) and the corrugated fins (5). Also, when the width ofthe heat exchange tubes (91) as measured in the front-rear direction isrepresented by W1 (mm) and the length (as measured in the front-reardirection) of contact areas where the left and right side surfaces ofthe heat exchange tubes (91) are in contact with the correspondingcorrugated fins (5) is represented by W2 (mm), preferably, a contractratio W2/W1; i.e., the ratio of W2 (the length (as measured in thefront-rear direction) of the areas of contact between the left and rightside surfaces of the heat exchange tube (91) and the correspondingcorrugated fins (5)) to W1 (the width of the heat exchange tubes (91) asmeasured in the front-rear direction), is 80 to 95%. Furthermore,preferably, the width W1 of the heat exchange tubes (91) as measured inthe front-rear direction is 10 to 20 mm, and the thickness H of the heatexchange tubes (91) as measured in the left-right direction is 1 to 1.8mm.

In each tube set (92) composed of the front and rear heat exchange tubes(91), preferably, the width S (as measured in the front-rear direction)of the clearance (95) formed between the heat exchange tubes (91)located adjacent to each other in the front-rear direction is 1.5 to 3.5mm. If the width S of the clearance (63) as measured in the front-reardirection is smaller than 1.5 mm, condensed water having been producedon the surfaces of the corrugated fins (5) and flowed into (as if it hadbeen drawn into) the clearance (95) between the front and rear heatexchange tubes (91) of each tube set (92) by means of surface tensionstagnates at the clearance (95) due to surface tension, which hinders adownward flow of the condensed water. If the width S of the clearance(95) as measured in the front-rear direction is greater than 3.5 mm,condensed water produced on the surfaces of the corrugated fins (5)becomes less likely to be drawn into the clearance (95).

The evaporator (90), together with a compressor and a condenser servingas a refrigerant cooler, constitutes a refrigeration cycle which uses achlorofluorocarbon-based refrigerant. This refrigeration cycle isinstalled in a vehicle, such as an automobile, as a car air conditioner.

In the evaporator (90) described above, while the compressor is ON, atwo-phase refrigerant of vapor-liquid phase having passed through thecompressor, the condenser, and an expansion valve enters the upper space(7A) of the refrigerant inlet header section (7) from the refrigerantinlet pipe (11); flows through the lower space (7B) of the same, thefront heat exchange tubes (91), the upper space (13A) of the firstintermediate header section (13), the lower space (13B) of the same, thelower space (14B) of the second intermediate header section (14), theupper space (14A) of the same, the rear heat exchange tubes (91), thelower space (8B) of the refrigerant outlet header section (8), and theupper space (8A) of the same; and flows out to the refrigerant outletpipe (12).

While flowing through the front and rear heat exchange tubes (91), therefrigerant is subjected to heat exchange with air flowing through theair-passing clearances between the tube sets (92) each composed ofadjacent heat exchange tubes (91). Then, the refrigerant flows out fromthe evaporator (90) in a vapor phase.

At that time, condensed water is produced on the surfaces of thecorrugated fins (5). Due to surface tension, the condensed water flowsinto the recesses (94) formed between the outer surfaces of the slopesportions (93) of the front and rear end walls (91 a) of each heatexchange tube (91) and the left and right edges of the correspondingcorrugated fins (5), as if the condensed water were drawn into therecesses (94). After that, the condensed water flows downward via therecesses (94). Accordingly, the evaporator (90) has an improvedcondensed water draining performance, whereby a drop in the performanceof the evaporator (1) is prevented.

INDUSTRIAL APPLICABILITY

The evaporator according to the present invention is suitable for use ina refrigeration cycle which constitutes a car air conditioner.

1. An evaporator comprising a pair of header tanks spaced from eachother in a vertical direction; a plurality of flat heat exchange tubeswhich are disposed between the two header tanks such that their widthdirection coincides with a front-rear direction and they are spaced fromone another in a left-right direction, opposite ends portions of theflat heat exchange tubes being connected to the corresponding headertanks; and corrugated fins each disposed between adjacent heat exchangetubes, wherein each of left and right portions of front and rear endwalls of each heat exchange tube has a straight slope portion whichinclines outward in the front-rear direction, toward a center portion ofthe heat exchange tube with respect to the left-right direction, and anangle formed between the slope portion and a left edge or right edge ofthe corresponding corrugated fin is 25 to 40 degrees.
 2. An evaporatoraccording to claim 1, wherein left and right side surfaces of each heatexchange tube are in contact with the corresponding corrugated fins; anda ratio of a length W2 (mm), as measured in the front-rear direction, ofareas of contact between the left and right side surfaces of the heatexchange tube and the corresponding corrugated fins to a width W1 (mm)of each heat exchange tube as measured in the front-rear direction is 80to 95%.
 3. An evaporator according to claim 1, wherein each heatexchange tube has a width of 10 to 20 mm as measured in the front-reardirection.
 4. An evaporator according to claim 1, wherein each heatexchange tube has a thickness of 1 to 1.8 mm as measured in theleft-right direction.
 5. An evaporator according to claim 1 wherein aplurality of tube sets each composed of a plurality of flat heatexchange tubes spaced from one another in the front-rear direction aredisposed between the upper and lower header tanks at predeterminedintervals in the left-right direction; each of the fins is disposedbetween tube sets located adjacent to each other in the left-rightdirection; and, in each tube set composed of a plurality of the flatheat exchange tubes, a clearance is formed between the heat exchangetubes located adjacent to each other in the front-rear direction, theclearance having a width of 1.5 to 3.5 mm as measured in the front-reardirection.
 6. An evaporator according to claim 1, wherein each heatexchange tube is provided in a flat hollow body composed of two pressedrectangular metal plates laminated and joined together; the two metalplates which constitute the flat hollow body are bulged outward so as toform the heat exchange tube such that the heat exchange tube is open atupper and lower ends thereof; each of front and rear walls of an outwardbulged portion of each metal plate which forms the heat exchange tube isstraight and inclines outward in the front-rear direction, toward athicknesswise center portion of the flat hollow body.
 7. An evaporatoraccording to claim 6, wherein, at a front edge of each flat hollow body,one of the two metal plates has a protrusion formed over the entirelength thereof such that a distal end portion of the protrusion projectsbeyond the other metal plate and toward the corrugated fin with whichthe other metal plate is in contact.